/Engine/Source/Runtime/Core/Public/Misc/MapErrors.h
Particle System {Actor} : Emitter actor has NULL ParticleSystemComponent property - please delete!: This warning is caused when there is a Emitter actor with a "None" ParticleSystemComponent. It is usually found in older maps where duplication was used to create the actor and can be fixed by deleting the actor causing the warning and creating a new one.
static [FLazyName](API\Runtime\Core\UObject\FLazyName) ParticleSystemComponentNull;